Best Fungicides?

MissCricket(5A)May 24, 2012

I've been growing roses for years, mostly hybrid teas, but I've never been able to beat back the black spot. That accursed black spot. How I hate it. I know my way around feeding, around insect infestations, around mildew, but every year this vile spore machine sits back and laughs at me.

It usually doesn't show up around here until August, but thanks to the unseasonably warm winter I'm seeing spots already. Since the fungus is starting its assault early I think I need bigger guns. Usually I just grab whatever's on sale at the local garden store since I'm on a slightly restrictive budget. Given that this year I'm going to be fighting this fight for the entire growing season I'm willing to spend a little more.

What tends to be most efficacious, and how often should I apply it? In the past I've aimed for every 2 weeks, should I apply more often? Should I apply a systemic along with a topical? Or should I just accept my inevitable defeat? On some level I've never really tried too hard to keep it away, because there never seemed to be any way to really succeed in keeping it away, but if it's going to be here for five months instead of the usual three it seems rather imperative to at least try to battle it.

I strongly recommend Bayer Advanced Garden Disease Control for Roses, Flowers, and Shrubs (that is a fungicide only--don't be tempted by the other Bayer 3-in-1 or all-in-one type products--you absolutely do not want them).

You will need to invest in a small hand-pump spray container--costs under $20 at Home Depot. Follow the directions on the Bayer Disease Control--if I remember correctly, 1.5 tbsp per gallon of water in the container (or something like that).

Make sure you have covered your arms and legs and feet etc. Some people take even more precautions.

Pick a MORNING when there is no breeze--important. You don't want a faceful of fungicide because a breeze suddenly turned your direction.

Spray anything that already has BS. It will kill the current BS, as well as act as a future preventative through its systemic action.

If you wish to start an active preventative program, spray all your rose every 2 weeks--whether they need it or not.

Myself, I buy only disease-resistant roses and I know my roses well enough that I know which ones will almost never need any spraying, which ones will sometimes have periodic problems, and which ones (very few in my garden) will regularly have BS problems. Thus when I spray, I spray only the ones that have regular BS problems. If the temps are right for BS, I may spray some of the roses that get periodic problems--or I may not. The ones that are very disease-resistant I do not spray unless I actually see a couple black spots on them--though I may not spray then either if my experience is that is about all they will get. I can live with a few blackspots as long as they are limited.

In other words, I may spray only about 1/3 to 1/2 my roses each time I spray. Other gardeners in different locales where there are more BS pressures may need to spray more of their roses on a regular basis.

I also usually limit my spraying to a few times in the spring and a couple times in the fall--both being times when the temperatures encourage the formation of blackspot. When it is really hot and dry in July and August, my roses rarely have BS problems--so I don't spray then. You would have to experiment to find out which months your roses need most and least protection from BS.

As a general rule for prevention, some rose gardeners spray every 2 weeks all growing season. You will have to decide for yourself if you want to spray that often.

There are no absolute rules in these matters. Hopefully my comments above will give you some options to try and see what works best for your region.

Your fungi will begin to develop a resistance to the Bayer by spraying it every week. You should alternate it with something. One of the best alternates is to simply mix in some Mancozeb/Pentathlon every 3rd or 4th spray. Or, simply go out and buy some old Ortho Funginex and spray that one week - but you'll have to spray one week later. Funginex (Ortho Garden Disease Control) only gives 1 week protection.

Here's a great article on spraying from the Rosemania website:2011 Spray Programs - American Rose magazine
They talk about Banner Maxx (propiconazole), but Bayer is more or less the same thing (tebuconazole) in a less concentrated form.

Regardless, it's important that you not spray too often and with the same thing. You may end up with BS that nothing can kill.

I'm with you miss cricket! Usually we do not even have roses yet, and this morning I sprayed for BS, and yes, I also use Bayer Disease Control every 2 weeks. Between the BS, mosquitos, and no rain, it should be an interesting summer.

Maude, by spraying every week you are just wasting chemicals and time, and putting an unnecessary burden on the environment. Spraying only Bayer (tebuconazole) every two weeks gives good control under the worst disease pressure. Maybe if there is a lot of active disease, you might make the second application after 7 days and then go to 14.

Rosetom, I don't understand the reasoning behind your statement, "Regardless, it's important that you not spray too often and with the same thing".

I agree that not spraying with the same thing (i.e. alternating sprays) lowers the probability of a resistant strain surviving and reproducing in your garden, but why would spraying once a week rather than twice a week (i.e. spraying more often) increase the probability of a resistant strain surviving and reproducing in your garden?

Thanks for the information, and thank god I asked...lol. It never occured to me that resistance could develop. The reason that I was doing this was because a bunch of the roses that I planted this spring are florist roses that I took from cuttings. I was very concerned about them making the transition from my window to the garden so I guess I was being overly cautious.

They are still alive though and I'm hoping that the spider mite problem I had indoors will disappear.

Oops, I meant to say, " why would spraying once a week rather than biweekly (i.e. spraying more often) increase the probability of a resistant strain surviving and reproducing in your garden?"

Mike,
Almost every fungicide recommendation - including the recommendations from the ARS and other articles about fungicides, state that you shouldn't increase the contact without rotating. Spraying the same spray once a week increases the contact exposure to the fungicide in much less time. The enhanced frequency is needless with something like the "-azoles," which are proven to provide 2-week protection.

What you're doing by spraying more frequently is allowing resistant spores to increase more frequently with no competition from non-resitant spores. The spores are living organisms - they will attempt to mutate, to evolve, and to produce more resistant strains if they are only exposed to one threat. If this threat is introduced more frequently, then that resistance will occur much faster and with greater magnitude.

That's assuming a regular spray regimen, though. You may be referring to an outbreak - in that case, repeated spraying in weekly intervals (or even more frequent) may do a good job in knocking down an outbreak. But it should probably be limited to a 3-spray period, total. It's not a prescription for a regular spraying regimen throughout the whole season.

Perhaps I should have made that distinction before making the statement I made. Even then, though, I would attempt to rotate something else immediately after the BS appeared to be in check. IMHO, a contact killer such as Mancozeb/Pentathlon or Daconil (in cooler temperatures) is best to knock down an outbreak. Something like that doubles as a rotation against developed resistance, too.

I spray once every two weeks - sometimes even longer. If during the longer durations, I notice some BS developing, I pull out the Pentathlon mixed with the Bayer. It stops the BS in its tracks, right then and there. Then I go back to the normal regimen of 2 weeks or even longer (when I get lazy, it rains, etc., etc.)

Just an FYI, but there are some other fungicides out there that do an excellent job - one even better than the Bayer: Compass. Unfortunately, it's extremely expensive because it's not allowed to be sold in small quantities. Heritage is close and cheaper (both are an oxystrobin-type anti-fungus fungus), but it seems to only last a week for me. Any of those, or the Funginex (Ortho Rosepride Disease Control) I mentioned earlier are good things to rotate - just to spray once in awhile to keep the BS from becoming resistant to the Bayer.

Of course, if you invest in the Compass, you should probably use that as your primary spray and let the Bayer be the mix-em-up rotator. Compass is such a severe anti-fungicide that they recommend a limit of only 4 applications per season. From what I experienced several years ago (you could buy it in 2oz quantities from Home Depot Landscaping before they closed the stores), it lasted about 4 weeks.

Spraying a fungicide such as tebuconazole more often than the recommended time interval may have undesirable growth effects on the roses through inhibiting gibberellin synthesis, reducing ethylene evolution and increasing cytokinin levels.

"Triazole compounds have both fungitoxic and growth-regulating properties [2]. In addition, they can also protect plants against various environmental stresses [3,4]. Triazoles affect the isoprenoid pathway and alter the levels of certain plant hormones by inhibiting gibberellin synthesis, reducing ethylene evolution and increasing cytokinin levels [5]. Previous works revealed the morphological and physiological changes associated with triazole-treatment in various plants, include the inhibition of plant growth, decreased internodal elongation, increased chlorophyll levels, enlarged chloroplasts, thicker leaf tissue, increased root to shoot ratio, increased antioxidant potentials and enhancement in alkaloid production [6-9]. From:http://idosi.org/abr/3(3-4)/11.pdf

Also the "Understanding fungicide resistance" article linked to below may be of interest.

I believe the limit of 4 applications per season for the strobilurin fungicide is because of concerns about resistance developing. They want users to alternate it strictly with a different type of fungicide.

The Bayer Disease Control package does not recommend rotation of fungicides. Probably it is because resistance is unlikely to develop in a small home garden. Resistance can develop with these triazole fungicides, but the odds go up greatly with massive agricultural use.

Regarding Henry's point, Banner Max propiconazole (sister chemical to Bayer tebuconazole) is known to retard growth in roses, and this is why the label says to spray at 14-day intervals. I have observed this effect by spraying only the left side of several roses with propiconazole, leading to shorter stems than on the other side. It's possible that weekly spraying with Bayer could do this, but not as dramatically.

Whee, that's a lot of info to process! Maybe I should have paid more attention in chemistry class...

I'm not about to yank healthy vigorous plants that are in some cases older than I am (I got them as hand-me-downs from my father's garden, I'm 28, Brandy, Jennifer Heart, Peace, JFK, Dynasty, Touch of Class and Double Delight are around 33.), so that option's out. Besides, I'm stubborn.

Lucky for me the local garden center had a big Memorial Day sale, so I got some Bayer and some Funginex. I think I'm going to set up set up a rotation schedule as rosetom suggested. I'll just have to keep close tabs on how much success I do or don't have. Now if only I could get a day that isn't windy and isn't likely to feature a raging downpour in the afternoon!

If you are 28 and have or are planning on having children, I suggest that you check into the safety of your selected spray materials (not on whether they will kill you tomorrow but what is known or not known about the long term effects on your family).

The quote given below from the Univ of Washington Botanic Gardens link below may be worth considering.

"When deciding whether to treat a garden problem with pesticides, the "Precautionary Principle" provides an important perspective:
"When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically.""

Try 1/4 cup bleach in 3 gallons of H20. Spray in the evening. Make sure to spray the soil and the surrounding area, even concrete, decking, etc.. I've had good luck with this and it's cheap. Also inhibits mildew.

In the alkaline clay soils that permeate the Midwest, bleach compounds the problem of incorrect (too high) soil ph. Bleach application will do one thing successfully--it will prevent iron uptake by the rose and probably result in chlorosis.

Yes, Pasadena has far different soil & weather than here. The original post was from a lady in Wisconsin, which is why I posted the cautionary note. I nearly wrecked an entire bed 3 years ago after I installed rain barrels that were recycled from a pool-care store. The barrels had housed bleach & even after several good rinses the residue that leached into the soil was pretty disastrous.

I feel that any mention of spraying roses with bleach solutions should mention the dangers involved (to the roses and people, pets, other friendlies) and contain recommendations on proper spraying safety procedures.

Blackspot hardly exists in Pasadena, and the rare outbreaks will dissipate when the weather normalizes, so I wouldn't look to Southern California for blackspot remedies. I can believe bleach would knock back powdery mildew, but so do many other home remedies that are much safer to handle. Bleach is more acutely toxic than any synthetic fungicide and poses a hazard to plants as well as gardeners.

A Risk Assessment Report (RAR) conducted by the European Union on sodium hypochlorite conducted under Regulation EEC 793/93 concluded that this substance is safe for the environment in all its current, normal uses.[24] This is due to its high reactivity and instability. Disappearance of hypochlorite is practically immediate in the natural aquatic environment, reaching in a short time concentration as low as 10Ã¢ÂÂ22 ÃÂ¼g/L or less in all emission scenarios. In addition, it was found that while volatile chlorine species may be relevant in some indoor scenarios, they have negligible impact in open environmental conditions. Further, the role of hypochlorite pollution is assumed as negligible in soils.

Bleach is used to disinfect drinking water, we wash our clothes with it, it leaves no residue and we even swim in it. How about the air around an indoor pool? Bleach solution (3 teaspoons per gal. H20 is the preferred method of commercially sanitizing food preparation surfaces and utensils. I don't know that the same could be said about ANY commercial anti-fungal product. Read up on it and decide for yourself.

I would rather use bleach than milk or other household product that does not work or some of the VERY toxic commercial fungicides. Just my 2 cents.

Right, there is little risk to the environment because it breaks down immediately. The risk to the person spraying it is inhalation or getting it in the eyes. The risk to the plant is burnt foliage if you don't use the right concentration.

Because they break down so readily, disinfectants such as bleach or TA 20 have limited value in the garden. You can't disinfect the outside world--bacteria and fungal spores are constantly blowing around or being carried around.

Concerning bleach and concentration. The recommendation of: "1/4 cup bleach in 3 gallons of H20" gives an available chlorine concentration around 267 ppm. This amount IS a high concentration compared to the "safe" drinking water and swimming pool examples.
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Drinking water has about 0.5 to 2 ppm available chlorine:http://www.newmadridcountyhealthdept.com/wands.html

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Swimming pools are about the same ("Check chlorine level in pool water at least daily with a pool testing set and
add this product as needed to maintain 0.6 to 1.0 ppm available chlorine." This is from the Clorex company:http://www.poolforum.com/pf2/archive/index.php/t-5852.html
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Concerning the comment: "Bleach solution (3 teaspoons per gal. H20 is the preferred method of commercially sanitizing food preparation surfaces and utensils."

H. Kuska comment: that mixture yields a ppm of 195. However, that amount is put on a surface not sprayed into the air!

In addition to short term high exposure problems, there are problems with long term low exposure problems with chlorine, see (since the original poster is from Wisconsin):

Simple. I have 3 fungicides I keep handy and use. Bayer fungicide, Ortho Rose Pride, Manzate. 1st weekend of every month I mix Ortho Rose Pride and Manzate and spray. Next weekend Spray Bayer. 2 weekends later Bayer again. I start in April and stop in mid November. Clean garden all spring, summer and fall. 1/3 of my garden are HT's, then I have a bunch of other roses that are black spot magnets (Austin, OGR, Flor. and a few others). I like seeing foliage from the top of my bush's to the bottom. I grow what I want to grow. Not what someone else want's me to grow.